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133. "Synergic Interface and Optical Engineering for High‐Performance Semitransparent Polymer Solar Cells"

Shi, Hui; Xia, Ruoxi; Sun, Chen; Xiao, Jingyang; Wu, Zhihong; Huang, Fei; Yip, Hin‐Lap; Cao, Yong 

Advanced Energy Materials, 2017, 71701121

~ 2017 ~


132. "Naphthalene diimide based n-type conjugated polymers as efficient cathode interfacial materials for polymer and perovskite solar cells"

Jia, Tao; Sun, Chen; Xu, Rongguo; Chen, Zhiming; Yin, Qingwu; Jin, Yaocheng; Yip, Hin-Lap; Huang, Fei; Cao, Yong 

ACS Applied Materials & Interfaces, 2017, 936070-36081

A series of naphthalene diimide (NDI) based n-type conjugated polymers with amino-functionalized side groups and backbones were synthesized and used as cathode interlayers (CILs) in polymer and perovskite solar cells. Because of controllable amine side groups, all the resulting polymers exhibited distinct electronic properties such as oxidation potential of side chains, charge carrier mobilities, self-doping behaviors, and interfacial dipoles. The influences of the chemical variation of amine groups on the cathode interfacial effects were further investigated in both polymer and perovskite solar cells. We found that the decreased electron-donating property and enhanced steric hindrance of amine side groups substantially weaken the capacities of altering the work function of the cathode and trap passivation of the perovskite film, which induced ineffective interfacial modifications and declining device performance. Moreover, with further improvement of the backbone design through the incorporation of a rigid acetylene spacer, the resulting polymers substantially exhibited an enhanced electron-transporting property. Upon use as CILs, high power conversion efficiencies (PCEs) of 10.1% and 15.2% were, respectively, achieved in polymer and perovskite solar cells. Importantly, these newly developed n-type polymers were allowed to be processed over a broad thickness range of CILs in photovoltaic devices, and a prominent PCE of over 8% for polymer solar cells and 13.5% for perovskite solar cells can be achieved with the thick interlayers over 100 nm, which is beneficial for roll-to-roll coating processes. Our findings contribute toward a better understanding of the structure–performance relationship between CIL material design and solar cell performance, and provide important insights and guidelines for the design of high-performance n-type CIL materials for organic and perovskite optoelectronic devices.


131. "Fabrication of high-performance and low-hysteresis lead halide perovskite solar cells by utilizing a versatile alcohol-soluble bispyridinium salt as an efficient cathode modifier"

Chen, Guiting; Zhang, Fan; Liu, Meiyue; Song, Jun; Lian, Jiarong; Zeng, Pengju; Yip, Hin-Lap; Yang, Wei; Zhang, Bin; Cao, Yong 

Journal of Materials Chemistry A, 2017, 517943-17953


130. "Effects of organic cations on the defect physics of tin halide perovskites"

Shi, Tingting; Zhang, Hai-Shan; Meng, Weiwei; Teng, Qiang; Liu, Meiyue; Yang, Xiaobao; Yan, Yanfa; Yip, Hin-Lap; Zhao, Yu-Jun;  

Journal of Materials Chemistry A, 2017, 515124-15129


129. "Combined optimization of emission layer morphology and hole-transport layer for enhanced performance of perovskite light-emitting diodes"

Meng, Fanyuan; Zhang, Chongyang; Chen, Dongcheng; Zhu, Weiguo; Yip, Hin-Lap; Su, Shi-Jian

Journal of Materials Chemistry C, 2017, 56169-6175


128. "Dual interfacial modifications enable high performance semitransparent perovskite solar cells with large open circuit voltage and fill factor"

Xue, Qifan; Bai, Yang; Liu, Meiyue; Xia, Ruoxi; Hu, Zhicheng; Chen, Ziming; Jiang, Xiao‐Fang; Huang, Fei; Yang, Shihe; Matsuo, Yutaka; Yip, Hin-Lap; Cao, Yong

Advanced Energy Materials, 2017, 71602333


127. "Interface design for high-efficiency non-fullerene polymer solar cells"

Sun, Chen; Wu, Zhihong; Hu, Zhanhao; Xiao, Jingyang; Zhao, Wenchao; Li, Ho-Wa; Li, Qing-Ya; Tsang, Sai-Wing; Xu, Yun-Xiang; Zhang, Kai; Yip, Hin-Lap; Hou, Jianhui; Huang, Fei; Cao, Yong

Energy & Environmental Science, 2017, 101784-1791


126. "Interface Engineering of a Compatible PEDOT Derivative Bilayer for High‐Performance Inverted Perovskite Solar Cells"

Bao, Xichang; Wang, Junyi; Li, Yuan; Zhu, Dangqiang; Wu, Ying; Guo, Peipei; Wang, Xuefei; Zhang, Yongchao; Wang, Jiuxing; Yip, Hin‐Lap; Yang, Renqiang

Advanced Materials Interfaces, 2017, 41600948


Interface engineering is an important aspect for the improvement of perovskite solar cells (PVSCs). The hole transport layer with good interface contact, transport capability, and matched energy level is indispensable and critical for high‐performance photovoltaic devices. Herein, anode interface engineering with an excellent compatible bilayer of poly(3,4‐ethylene dioxythiophene):poly(styrenesulfo‐nate)/poly(3,4‐ethylene dioxythiophene) (PEDOT:PSS/PEDOT) doped with grafted sulfonated‐acetone–formaldehyde lignin (PEDOT:GSL) via a low‐temperature and water‐soluble process is presented. As a water‐processable interface material, PEDOT:GSL exhibits higher conductivity, as well as better structural and electronic homogeneities compared with PEDTO:PSS. Consequently, the PEDOT:PSS/PEDOT:GSL bilayer with tuned energy level, optical properties, and the combination of the trap passivation of GSL at the anode/perovskite interface can greatly improve charge extraction ability and reduce the interface recombination. Simultaneously, the homogeneous perovskite film is fabricated through optimizing the annealing process. The device with the power conversion efficiency up to 17.80% is achieved, with 32.6% improvement compared to PEDOT:PSS‐only device (13.42%). Our success to achieve high‐performance inverted PVSCs provides new understanding of PEDOT:PSS, and also new guidelines for anode interface engineering to further advancement of PVSCs. This promising approach paves the way to realize solution processable highly efficient PVSCs for potential practical applications.

125. "Poly (3, 4‐Ethylenedioxythiophene): Methylnaphthalene Sulfonate Formaldehyde Condensate: The Effect of Work Function  and Structural Homogeneity on Hole Injection/Extraction Properties"

Li, Yuda; Liu, Meiyue; Li, Yuan; Yuan, Kai; Xu, Lijia; Yu, Wei; Chen, Runfeng; Qiu, Xueqing; Yip, Hin‐Lap

Advanced Energy Materials, 2017, 7, 1601499

Poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is widely used as hole injection/extraction material in organic optoelectronics. However, there still exist drawbacks for PEDOT:PSS such as low work function (WF), poor structural and electrical homogeneity. To solve these problems, methylnaphthalene sulfonate formaldehyde condensate (MNSF) is applied, which has excellent dispersion property, branched chemical structure, and low cost, as dispersant and dopant instead of linear PSS to prepare PEDOT:MNSF. The hole injection/extraction capability of PEDOT:MNSF is systematically studied in organic optoelectronic devices. PEDOT:MNSF‐1:6 exhibits unexpected high device performance with a maxima current efficiency of 33.4 cd A−1 in blue phosphorescent organic light‐emitting diode and a power conversion efficiency of 13.1% in CH3NH3PbIxCl3−x‐based inverted perovskite solar cell, respectively. Compared with PEDOT:PSS, the relatively higher efficiency of PEDOT:MNSF‐1:6 is attributed mainly to its higher WF of 5.29 eV, structural and electrical homogeneity. Our research displays a promising future of MNSF as a cheap and widely available alternative of PSS. Moreover, a clear map is provided for the design of dopant for PEDOT considering the structure of dopant.


124. "High‐performance color‐tunable perovskite light emitting devices through structural modulation from bulk to layered film"

Chen, Ziming; Zhang, Chongyang; Jiang, Xiao‐Fang; Liu, Meiyue; Xia, Ruoxi; Shi, Tingting; Chen, Dongcheng; Xue, Qifan; Zhao, Yu‐Jun; Su, Shijian; Yip, Hin‐Lap; Cao, Yong

Advanced Materials, 2017, 29, 1603157

Adding 2‐phenoxyethylamine (POEA) into a CH3NH3PbBr3 precursor solution can modulate the organic–inorganic hybrid perovskite structure from bulk to layered, with a photoluminescence and electroluminescence shift from green to blue. Meanwhile, POEA can passivate the CH3NH3PbBr3 surface and help to obtain a pure CH3NH3PbBr3 phase, leading to an improvement of the external quantum efficiency to nearly 3% in CH3NH3PbBr3 LED.


123. "Thermally stable high performance non-fullerene polymer solar cells with low energy loss by using ladder-type small molecule acceptors"

Li, Qing-Ya; Xiao, Jingyang; Tang, Lu-Ming; Wang, Hua-Chun; Chen, Ziming; Yang, Zhiyong; Yip, Hin-Lap; Xu, Yun-Xiang

Organic Electronics, 2017, 44, 217-224


Two ladder-type small molecule acceptors IDT-BT-R and IDT-BT-R-CN are utilized in non-fullerene polymer solar cells by pairing with PTB7-Th as donor polymer, in which PTB7-Th:IDT-BT-R solar cells achieve high performance up to 8.3% with high voltage of 1.02 V and low energy loss of 0.59 eV. Thermal annealing triggered local rearrangement of ladder-type molecules in n-type phases of bulk heterojunction films, increased their absorption abilities and electron transport properties, therefore resulting in improved short-circuit current densities (Jscs) and fill factors (FFs), in contrast to fullerene-based solar cells which suffered from extensive aggregation of fullerenes upon annealing. The outstanding thermal stability, high performance and low energy loss demonstrated here show great potential of non-fullerene polymer solar cells.

122. "General design of self-doped small molecules as efficient hole extraction materials for polymer solar cells"

Xue, Yuyuan; Guo, Peipei; Yip, Hin-Lap; Li, Yuan; Cao, Yong

Journal of Materials Chemistry A, 2017, 5, 3780-3785

The development of high performance hole transport materials (HTMs) without a chemical dopant is critical to achieve long-term device durability. The general design of self-doping materials based on a phenolamine structure with strong electronic spin concentration is reported for the first time. A phenol-enhanced self-doped mechanism is also proposed. Compared to their precursors, dimethylphenolamine derivatives, TBP-OH4, TPD-OH4 and Spiro-OH8, displayed much higher spin concentration in their neutral states. Phenol acts as a hole trap in the traditional concept, however, the films of TBP-OH4, TPD-OH4 and Spiro-OH8 exhibited higher conductivities than those of methoxyl precursors. Meanwhile, phenolamine derivatives have good solublility in polar organic solvents and show good solvent resistance in chlorobenzene. Considering the relatively good band alignment, film-formation and solvent resistance against chlorobenzene, Spiro-OH8 and TPD-OH4 exhibited comparable performance with that of PEDOT:PSS-4083. Most importantly, a new generation of self-doped systems based on a phenolamine structure might provide new insight in developing efficient HTMs for organic electronics.


121. "Amino-functionalized conjugated polymer electron transport layers enhance the UV-photostability of planar heterojunction perovskite solar cells"

Li, Dan; Sun, Chen; Li, Hao; Shi, Hui; Shai, Xuxia; Sun, Qiang; Han, Junbo; Shen, Yan; Yip, Hin-Lap; Huang, Fei; Wang, Mingkui

Chemical Sciences, 2017, 8, 4587-4594

In this study, for the first time, we report a solution-processed amino-functionalized copolymer semiconductor (PFN-2TNDI) with a conjugated backbone composed of fluorine, naphthalene diimide, and thiophene spacers as the electron transporting layer (ETL) in n–i–p planar structured perovskite solar cells. Using this copolymer semiconductor in conjunction with a planar n–i–p heterojunction, we achieved an unprecedented efficiency of ∼16% under standard illumination test conditions. More importantly, the perovskite devices using this polymer ETL have shown good stability under constant ultra violet (UV) light soaking during 3000 h of accelerated tests. Various advanced spectroscopic characterizations, including ultra-fast spectroscopy, ultra-violet photoelectron spectroscopy and electronic impedance spectroscopy, elucidate that the interaction between the functional polymer ETL and the perovskite layer plays a critical role in trap passivation and thus, the device UV-photostability. We expect that these results will boost the development of low temperature solution-processed organic ETL materials, which is essential for the commercialization of high-performance and stable, flexible perovskite solar cells.


120. "Solution-processed organic tandem solar cells with power conversion efficiencies> 12%"

Li, Miaomiao; Gao, Ke; Wan, Xiangjian; Zhang, Qian; Kan, Bin; Xia, Ruoxi; Liu, Feng; Yang, Xuan; Feng, Huanran; Ni, Wang; Wang, Yunchuang; Peng, Jiajun; Zhang, Hongtao; Liang Ziqi; Yip, Hin-Lap; Peng, Xiaobin; Cao, Yong; Chen, Yongshen

Nature Photonics, 2017, 11, 85-90

An effective way to improve the power conversion efficiency of organic solar cells is to use a tandem architecture consisting of two subcells, so that a broader part of the solar spectrum can be used and the thermalization loss of photon energy can be minimized1. For a tandem cell to work well, it is important for the subcells to have complementary absorption characteristics and generate high and balanced (matched) currents. This requires a rather challenging effort to design and select suitable active materials for use in the subcells. Here, we report a high-performance solution-processed, tandem solar cell based on the small molecules DR3TSBDT and DPPEZnP-TBO, which offer efficient, complementary absorption when used as electron donor materials in the front and rear subcells, respectively. Optimized devices achieve a power conversion efficiency of 12.50% (verified 12.70%), which represents a new level of capability for solution-processed, organic solar cells.

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